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Old 11-01-2010, 05:57 PM   #15
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Originally Posted by dznf0g View Post
Since tire pressure rises approx. 1 degree for every 10 degrees of (ambient) temp rise, if you take a reading at 6AM at 60 degrees and wait till 2PM to take another reading at 100 degrees you'll be off by about 4 degrees in your calculations.
I think you mean 1 lb./10 degrees. I question that number that because direct sun on the tires makes them hotter because they are black. I find the tires in the sun before I go anywhere are about 3 to 4 lbs. higher (this sentence makes me wonder why tires aren't spelled "tigher") than the tires in the shady side. I seem to remember someone once posted the pressure increases more than 1 lb./10 degrees, but that was a couple of years ago and I don't know where it was posted.

Cold pressure is what you are supposed to fill the tires atóbefore drivingóbut the position of the sun and the time of day changes things. Here in the southwest we often have 40˚ swings in temp during the day and 65 lbs at dawn (maybe 40˚, 75˚ or more in the afternoon) may be somewhat higher before driving, and tires on the south side while driving may be 10 lbs. or more higher than starting out. Driving south or north or up or down in altitude may mean significant swings in ambient temps. Some early mornings we have 68 lbs. in Load Range E tires and be up to 81 lbs. by afternoon. This means my TPMS monitor starts beeping and red lights come onóI check the pressure, cancel the warning, and keep driving. Then another tire does the same thing and so do I. When I do stop, I let a pound or two out of the tire. My TPMS reads 3 lbs. differently than my hand held pressure gauge and about 2 lbs. difference with the gauge on the compressor.

I err on the side or more pressure rather than less since the wheels and tires can take it better than the tires take lower pressure. This means using the shady side as the norm, doing it before the sun starts to warm up the air and the tires, and using the gauge that reads lowest. After looking at weight tables for my tires and the weight on each wheel, 68 lbs. early morning cold pressure seems to be the right spot.

There are so many variables that while it's good to be perfect, perfection as always is elusive.

After reading what feels like a gazillion tire posts on a thousand tire threads it's hard not to start screaming. Just about every brand ST tire has been criticized. It's been said Carlisles were once good, but cheapened. I think Towmaster was also criticized as being whatever they could get from China. Maxxis owners have had some problems and it's been said they are presently backordered. It's been said Marathons are now made in China, but are all made in the US, or maybe Canada. And all ST tires have been criticized as having low standards. While Tire Rack has ratings of tires on its website, last time I looked, did not rate ST tires. Whenever the subject of ST tires comes up at campgrounds or at tire shops, everyone seems to agree ST tires are junk. Of course, there's been plenty of criticism of LT tires.

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Old 11-01-2010, 11:32 PM   #16
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Gene,
you're correct about the sun thing. I am just pointing out the article makes sense in theory and I was assuming all equal temps in the morning. (ie. shortly after sunup before any "artificial heating" by the sun) Or at night, just before bedtime. My observation is that sunny side is worth about 2 - 3 PSI additional rise in my northern climate in summer. This has to be taken into account with your measurements throughout the day of travel as well. I would ignore a high pressure alarm on the sunny side if the shady side is within that 10% bogey. (but watch the numerical readout in case there is a bearing or brake issue which keeps the pressure rising) My Doran high pressure alarm comes in at 25% above my preset. That means at 65PSI, I would have to be at 81 PSI to get an alarm. I think that's more than a sun effect, or normal tire heating. Or does it mean that LREs run at 65 PSI heat up MORE than LRDs at 65 PSI? Or, in your "vertical" area, are you getting a lot of brake heating? It may also be different down south. I've heard of wild temp swings from night to day in the desert, but don't have much experience there. Up here we get, maybe a 25 degree swing from night to day in summer on average.

Yes, it was supposed to be 1lb/10 degrees....sometime the brain runs faster than the fingers on the keyboard.
I have studied TPMS on TVs and cars an I am comfortable that 1lb/10degrees is pretty close. However, I have also noticed that my Marathons seem to be a little more than that. Hmmmm...could something in their construction make them heat more than other tires. They are the only brand that I have had with TPMS, so I don't know.

Wow, I have never seen the type of rise that you have experienced. I run at 65 PSI cold, and the highest I have ever seen is 72 PSI at about 85 - 90 degrees ambient, and 7640 lbs (per scales) on the axles. (LRD tires). At these temps. I see only about a 4 PSI rise on the TV.

I'm not saying, this is the answer. Just saying that it makes sense and I am going to experiment with it next spring. I may have one more trip before I retire the Marathons and go to LREs.

One of the points of the article was the "counter intuitiveness" of letting out air for a "hot tire". I'm not saying it's true at this point, but the author states that's just opposite of the right thing to do.
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Old 11-02-2010, 12:11 AM   #17
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2Air,

I missed your post due to the page break. As usual, I find little to disagree with in your comments. That being said, I'm not sure that the "old school" approach is expired with whatever changes have taken place with tire technology. There is something we're all missing in this "ball of yarn". Yes, there are some substandard tires out there, but it can't be all brands, and all STs. Various posts on various forums would indicate that is the case. I've never had a blow out in 35 years of towing. Did throw a chunk of tread once on a too old tire in my inexperienced youth.

I just can't get to the place that LREs should be run at sidewall pressures on a trailer prescribed to have LRDs at 65 PSI (or arguably lower), for fear of beating the trailer up. (of course at 7640 lb combined axle weight for 4 tires in my case). Most everyone agrees that there is an imperceptible difference in sidewall flexibility between a LRE and an LRD, but a 15 psi difference will make a huge difference in primary shock absorption.

We can demonstrate this by taking our unloaded car or light truck and running it down a rough road at the door jamb recommended pressure and then filling to sidewall max, and feel the difference. I know that's elementary, but again, we're missing something in many of these tire failure accounts.

However, since so many of us are now equipped with TPMS, it might be time for some data gathering?
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Old 11-02-2010, 05:58 AM   #18
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Hi,

Not sure how others are finding the quality but after a couple seasons on these Carlisle's I'm very happy. The wear pattern is completely even and there are no bubbles on the sidewalls. I run the tire pressure at 65psi and check them before and after each trip. So far so good.
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Old 11-02-2010, 07:44 AM   #19
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Putting #80 in your tires is like towing with a 1 ton.
Not sure about that - seems to me I have read that it is your trailer's primary suspension that mainly determines the sort of ride your trailer will get and that the effect of the tires is minimal.

Can anyone shed light?

Brian
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Old 11-02-2010, 07:52 AM   #20
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i agree passenger/truck tires can ride very differently with just a few psi of change.

and while p/lt tires are capable of handling the max sidewall pressure...

VEHICLE makers specify tire pressures very specifically in oem sizes, typically well below max psi.

trailer axles and tires aren't placed at the perimeter and don't deal with slip angles, cornering or traction issues that motor vehicles do.

Quote:
Originally Posted by dznf0g View Post
...I just can't get to the place that LREs should be run at sidewall pressures on a trailer prescribed to have LRDs at 65 PSI (or arguably lower), for fear of beating the trailer up. (of course at 7640 lb combined axle weight for 4 tires in my case). Most everyone agrees that there is an imperceptible difference in sidewall flexibility between a LRE and an LRD, but a 15 psi difference will make a huge difference in primary shock absorption...
the 'advantage' if there is any, with sticking to ST tires is that they come in 3 flavors based on expected LOAD.

C D and E are distinctions that matter and should be considered carefully.

on a rig like vin's 30 slide which is the heaviest stream on 4 wheels, there is some logic in choosing Ez over Dz.

but for the most part sticking 2 the a/s oem size/rating/inflation is straight forward/clear/sensible.

a trailer spec'd with Cz (inflated to 50 psi) is NOT improved by going to Ez run at 50 psi.

the same is true for the majority of modern units with oem Dz run at 65 psi.

the notion of Ez somehow being better or an UPgrade is baseless in almost all trailer situations.

Ez do not have more ply or more layers of rubber/belts.

the sidewalls appear equally supple in D and E rated versions before mounting.

they are built to handle HIGHER air pressure thereby supporting higher loads.

but running them at significantly lower pressures (40-55 psi) negates the higher load capacity and introduces negatives...

more sidewall/belt flex, more side wall motion, less stability (resistance to sway), more heat, altered contact patch and so on...

in the a/s world, it is best to stick with the factory spec'd tire rating (and inflations) in almost all situations.

heavy trailers, folks who wanna tow OVER 65 mph or folks towing in desert HEAT...

are a few examples where E rated may be useful.

and those folks need to understand they are trading ride quality (softness) for other features (speed, less heat, more load bearing)

my experience with ST tires (canadian and chinese and thai') has been good (documented in another thread)

the tires have all performed as expected and with proper attention to the basics.

failures do happen

but separating out the failures based on inherent tire defects

from the 1000s of failed valve stems, underinflated, abused, old tires, and is problematic.

add to that the country of origin hate/bashing, and the repetitive negative posting by a small # of people,

and selecting new tires becomes overly complex.

cheers
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Old 11-02-2010, 08:22 AM   #21
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Originally Posted by 2airishuman View Post

a trailer spec'd with Cz (inflated to 50 psi) is NOT improved by going to Ez run at 50 psi.

the same is true for the majority of modern units with oem Dz run at 65 psi.

the notion of Ez somehow being better or an UPgrade is baseless in almost all trailer situations.

Ez do not have more ply or more layers of rubber/belts.

cheers
2air'
I believe these statements are 100% correct, and tire retailers have told me the exact same thing.

It is my opinion too many Airstreamers go to E rated tires believing them to be an upgrade, when if fact they are not if the extra weight capacity is not needed.
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Old 11-02-2010, 09:26 AM   #22
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Primary shock absorbers on any vehicle or trailer are the tires. Secondary shock absorbers are hydraulic shocks. Springs/torsion rubber are not "shock absorbers" per se, but rather are there to suspend loads and allow controlled "movement" of components (and thus extend vehicle component operating life) and provide load "comfort". It could be argued that springs do absorb some shock, and that's true, but by definition they are not classified as "absorbers". Just watch those vehicles with worn shocks and struts going down the road. Road shock isn't being absorbed, it is being eventually dissipated through cyclical spring harmonics. That is "brakes and suspension 101", the very first automotive class I took, low those many years ago.
Yes, LREs have no more physical plys nor are "stiffer", but the belts/strands may be thicker/larger in diameter and/or may be of different material. This MAY allow more tearing strength (ie. tread separation, pothole bruising resistance, etc.) I have heard no one say that the rubber is any different in composition, so I don't believe they would have any greater resistance to heat delamination nor UV resistance, etc.

Given all that, I am struggling to believe that LREs run at 65 PSI are going to run at any significantly different temp, contact patch area or sidewall profile given the same loads and environmental inputs, than LRDs. Time will tell. That's why I'm dragging up this conversation...AGAIN. I think we should gather some accurate DATA, not "war stories".

It is my belief that be it LRD or LRE, since the sidewall stiffness and tread cord stiffness differential is negligible, the only variable is air pressure. Air is the ONLY component of the suspension holding the vehicle off the road. (OK, don't get nit picky here...tire has small influence) Basically, the tire's only purpose is to contain the air, protect the air from escaping due to road shock/hazard and provide firm contact consistent with the pavement. Air does the work of "lifting" and absorbing shock.

I THEORIZE (at this point) that really the only advantage to moving to LREs are (all other environmental/load inputs being equal, and not introducing brand quality into the mix):

1) perhaps a greater resistance to tread separation due to road shock and bruising
2) perhaps a greater amount of time, once a eminent tire failure is indicated by TPMS, to get off the road before total separation/destruction. (because of stronger belt material)

I don't consider the swap to be an upgrade or "mod", but rather, and only perhaps, a greater margin of protection and security against SOME of the hazards of pavement pounding.

My only concern is heat and the effect of running LREs at 65PSI instead of 80 PSI. That's where I need to see data. And I'm willing to give it a go and see what's up.
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Old 11-02-2010, 10:06 AM   #23
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the primary/only documented feature of Ez is extra load rating when properly inflated.

none of the manufacturers claim more protection from belt/tread issues or road hazards or slower leak down times.

IF there were other benefits, no doubt the manufactures WOULD promote them in their adverts.
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having run years and 1000s of miles with D and and now E rated ST tires...

i have observed no difference in tire temps (d/65psi, e/70psi) during hot or warm weather, using infrared readings or tmps info.

with 3 axles my unit is well within the load rating for either and clearly the 34 does not need Ez.

i have yet to determine if they provide any greater durability/mileage.

cheers
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Old 11-02-2010, 10:29 AM   #24
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Thanks 2air - you have stated what I have been trying to find out for the last year. Weather or not I need to go to an e rated tire. I think I will stay with Dz and now try to figure out which is the best tire for the $$$$$. I am gong to install a TPMS with the external sensors (metal valve stems). I think the "being able to change out the battery myself" instead of the internal sensor is my choice. Also, I can move them from TV to TV and TT to TT without going to the tire shop.
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Old 11-02-2010, 10:48 AM   #25
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Thanks, 2 air,

You may well have answered the temp question. Although not with hard data...but I think you're at least as anal retentive as I am and I trust you observations
I too am well within the load limits of LRDs and only ASSUME that IF IN FACT, LREs have larger diameter strands and/or different materials in their belt and sidewall material to facilitate higher pressures and loads, that they would be more resistant to "stretching" and tearing when a failure or rupture starts to occur, especially at 65 psi, where the force on the failure point would be below what it would be at 80 PSI. (not sure I'm stating that point clearly)

I assume you're running 65 PSI on your LRDs? Marathons, I seem to recall from some other post?

Have you observed and can you share your observations relative to "normal" temp rises in varying conditions? (ie: differing regional climates, sunny side differentials, mountains and long downhill runs, brake heating effect etc?
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Old 11-02-2010, 10:57 AM   #26
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the primary/only documented feature of Ez is extra load rating when properly inflated.

none of the manufacturers claim more protection from belt/tread issues or road hazards or slower leak down times.

IF there were other benefits, no doubt the manufactures WOULD promote them in their adverts.
_________

having run years and 1000s of miles with D and and now E rated ST tires...

i have observed no difference in tire temps (d/65psi, e/70psi) during hot or warm weather, using infrared readings or tmps info.

with 3 axles my unit is well within the load rating for either and clearly the 34 does not need Ez.

i have yet to determine if they provide any greater durability/mileage.

cheers
2air'
I have a feeling the reason we can't get detailed pressure clarifications from mfrs., especially relative to the industry/govt. pressure charts, as well as more clearly stated benefits and features of various tire models (LRD vs. LRE in this case) is spelled PRODUCT LIABILITY! That also affects their claims and adverts too, I believe. I also believe that is why mfrs. and dealers "default" to stating max. sidewall pressure are appropriate only. Keeps them out of trouble, because "we all lie or ignore" true loads, speeds,mechanical condition of the chassis, maintenance etc.....

THE TRUTH IS OUT THERE! (somewhere)
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Old 11-02-2010, 12:44 PM   #27
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I would concur with 2air that running E's rather than D's or C's because they are stronger is not the real reasons why you should go to E's. I went to E's due to the weight of my heavy slide out and I felt that the reserve capacity I get (I think it was approx 300 lbs or so per tire @ 80 psi) was worthwhile. If it wasn't for that fact I'd still be using D's.

I did pick Maxxis over other brands due to the nylon cap that wraps the belts and is distinctive in Maxxis in that it minimizes belt squirm and its resultant heat generation. It's a concept used in high speed tires produced for Europe where speed limits are much higher.

So far we finished year 3 of service with no issues. My Canadian built Marathon's almost lasted four with one tire throwing a chunk of thread after 3 years and 10 months of service. End of next year will be a decision point for me as to either replace the Maxxis set for 2012 or go one last season and get 5 years out of them. We will see.

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Old 11-02-2010, 12:57 PM   #28
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I did pick Maxxis over other brands due to the nylon cap that wraps the belts and is distinctive in Maxxis in that it minimizes belt squirm and its resultant heat generation. It's a concept used in high speed tires produced for Europe where speed limits are much higher.

Jack
Jack,

TowMaster ST tires also have this nylon belt. So far, I've had a set of each, TowMasters, and Maxxis, and wore them out without a failure.
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